Method for processing of strip metal in a continuous manner to remove undesired curvature

ABSTRACT

Razor blade strip steel 0.2 inch wide and 0.0015 inch thick is transferred at a 30 foot per minute rate sequentially through a hardening furnace, an air-cooled tubular transition zone, a quench unit, a freeze unit, a tempering furnace, and a continuous inspection station to a takeup reel. The vertical position of the quench unit relative to the transition zone is adjustable so that a differential stress may be applied to the steel strip to prevent or minimize a dish condition in the processed strip.

United States Patent Inventor Thomas J. Rum

South Boston, Mass.

Appl. No. 833,211

Filed Jan. 31,1969

Patented Oct. 26, 1971 Assignee The Gillette Company Boston, Mass.

METHOD FOR PROCESSING OF STRIP METAL IN A CONTINUOUS MANNER TO REMOVEUNDESIRED CURVATURE 6 Claims, 5 Drawing Figs.

US. Cl 148/131, 148/128,148/153 Int. Cl C2ld 1/18 Field of Search148/131,

[56] References Cited UNITED STATES PATENTS 3,148,093 9/1964 Williams eta1. 148/131 Primary Examiner-Richard 0. Dean Attorney-Willis M. ErtmanABSTRACT: Razor blade strip steel 0.2 inch wide and 0.0015 inch thick istransferred at a 30 foot per minute rate sequentially through ahardening furnace, an air-cooled tubular transition zone, a quench unit,a freeze unit, a tempering furnace, and a continuous inspection stationto a takeup reel. The vertical position of the quench unit relative tothe transition zone is adjustable so that a differential stress may beapplied to the steel strip to prevent or minimize a dish condition inthe processed strip.

METHOD FOR PROCESSING OF STRIP METAL IN A CONTINUOUS MANNER TO REMOVEUNDESIRED CURVATURE This application is a division of my copendingpatent application Ser. No. 586,880, filed Oct. 14, 1966, now U.S. Pat.No. 3,466,022.

This invention relates to the processing of metal and more particularlyto the processing of strip metal in a continuous operation in a mannerto remove undesired curvature in the metal strip that extendstransversely of its length.

In the processing of strip metal, of the type intended for use in razorblades, for example, a dish condition (curvature in the metal striptransversely of its length) may be produced during the process of theheat treatment of steel. Such a dish condition in the metal stripcreates a particular problem related to the process of sharpening theedge of the strip to a shaving edge, as the dish condition efiectivelyoffsets the edge of the metal strip to be sharpened relative to thesupported body of the strip and the sharpening equipment so that aninferior sharpening process results.

The cause of such a dish condition in stainless steel strip is believedto result from an imbalance in the chemical composition and/ormicrostructure of the steel strip produced during the rolling process,specifically a difference in the amount of carbon and/or the size anddistribution of carbides present at the two surfaces of the steel strip.During the best treatment process, a difference in the resulting carboncontent of the austenite at the opposite surfaces of the strip resultsin a differential expansion (or contraction) of one surface of the striprelative to the other, and the resulting dish condition.

Accordingly, it is an object of the invention to provide novel andimproved methods and apparatus for removing a dish condition from stripmetal in a continuous processing operation.

In accordance with the invention, a dish condition is removed from asteel strip by subjecting the surfaces of the strip to a stressdifferential as austenite is being converted to martensite, the striphaving passed through a hardening furnace but prior to the quenching ofthe strip during the hardening process. In the preferred embodiment ofthe invention, this stress differential condition is produced by bendingthe strip over a relatively sharp edge surface when the austenite tomartensite conversion is still progressing.

In such continuous process, stainless steel strip, after passage throughan austenitizing furnace in which it is subjected to a temperature ofabout 2,000 F. to form austenite has its temperature reduced at acontrolled but relatively rapid rate to form martensite. When thetemperature of the strip reaches approximately 320 F. (the martensite toaustenite transformation still progressing) the strip is subjected tomechanical working if a dish condition is detected to exist. Thismechanical working is imposed on the steel strip just prior to entryinto a quench device and comprises subjecting the strip to an abruptchange in direction by bending it over a relatively sharp edge. In thepreferred embodiment, a transition zone between the furnace and thequench unit is an aircooled tubular element that includes a guidestructure of low thermal conductivity which guides both the edges andbottom surface of the strip. In the absence of dish, the horizontalstrip support surface of the guide structure is aligned with thecorresponding support surface of the quench unit. Where a dish conditionis detected, the position of the quench unit relative to the guidesurface in the transition zone is changed, preferably by lowering thequench unit, so that the strip is stressed as it passes over the edge ofthe guide structure at the end of the transition zone and also furtherstressed as the strip is again deflected through contact with the quenchunit.

This processing of strip steel in this manner enables reduction of thedish condition to within a process limit of 0.0007 inch over a stripwidth of 0.193 inch and to a corresponding limit for strip of differentwidth. In a process line where a dish sensor is employed, the positionof the quench unit relative to the transition zone may be controlledautomatically to produce hardened steel razor blade strip that issubstantially flat.

Other objects, features and advantages of the invention will be seen asthe following description of a particular embodiment thereof progresses,in conjunction with the drawings in which:

FIG. 1 is a block diagram of a steel-strip-hardening process line asused in the practice of the invention;

FIG. 2 is a diagrammatic perspective view of the transition between thetransition zone and the quench unit;

FIG. 3 is an end view of the quench unit and its support arrangement isused in the practice of the invention;

FIG. 4 is a side view of the apparatus shown in FIG. 3; and

FIG. 5 is a sectional view of the quench unit taken along the line 5-5of Fig. 4.

A processing line for treating stainless steel strip in a hardening andtempering operation to provide a strip of suitable metallurgicalcharacteristics capable of having formed thereon a durable, high-qualityshaving edge is shown diagrammatically in FIG. I. That processing lineincludes a supply reel 12 from which the strip 10 is taken for transfersequentially through a hardening furnace 14, an air-cooled transition(fourth) zone I6, a quench unit 18, a freeze unit 20, a temperingfurnace 22, and a continuous inspection station 24 to a takeup reel 26.The s trip 10 processed in this line is in the order of 0.2 inch wideand 0.00l5 inch thick. The steel employed in the preferred embodimenthas the following composition range:

Carbon (LN-0.44% Chromium l3.0l4.0% Manganese Gib-0.50%

Silicon (XXI-0.50% Molybdenum I.l5-l.35%

the balance being essentially iron.

In the processing operation, the strip 10 is advanced at a constant rateof about 30 feet per minute and is heated to a temperature ofapproximately 2,000 F. in furnace I4. At the output of the furnace, thesteel is subjected to an air-cooled environment so that its temperatureis about 320 F. at the end of tubular zone 16. This fourth zone tube mayvary in length, a 16 inch length being satisfactory in this system suchthat the austenite to martensite conversion begins in this unit and isstill in progress at the exit end of tube 16. The strip is then furthercooled by passage through a water-cooled quench block assembly 18 andthen a freeze cooling unit 20 which is operated at approximately F. Thesteel is then passed through tempering furnace 22, which is maintainedat approximately 500 F., and then through inspection station 24 wherethe quality of the processed steel in inspected. The heat treated steelis then wound on takeup reel 26.

The vertical position of the quench unit relative to the output of thefourth zone is adjustable as indicated in Figs. 3 and 4. That assemblyincludes a table 50 on which a quench block structure 52 is supported.As indicated in Fig. 5, that quench block structure includes a body 54which defines a passage 56 to which are connected inlet and outlet tubes58 for the flow of cooling water through the body. Supported on the bodyis a series of lower quench plates 60 held in place by clamp elements62, and a corresponding series of upper quench plates 64. These quenchplates in the this particular embodiment are manufactured of carbide(Carboloy grade 907 and each quench plate includes a central ridge 66which contacts the upper surface of the steel strip 10 (not shown inFig. 5) as it moves over the series of lower plates 60. The ends of thequench plate ridges 66 are radiused in the order of 0.025 inch andprovide a smooth transitional surface at the entry of the strip to thequench unit. At the forward end of the quench block base 54 there ismounted an upstanding bracket 70 that receives an adjustment screw 72and has a stop member 74 secured to its end. A lock nut 76 cooperateswith bracket 70 to lock screw 72 in position so that the stop member 74may hold the series of upper quench plates in the desired positionrelative to the body 54.

The quench block unit is coupled to table 50 by side plate elements 80,82 which are secured to the sides of the base 54 of the quench block bymeans of screws 84. Projecting laterally from the platform 50 are twoarms 85, each having an upstanding bracket 86 which receives anadjustment screw 88 that is coupled respectively to the blocks 80 and 82through a universal joint structure 90. By movement of the screws 88,the lateral position of the quench block assembly on the platform 50 maybe adjusted. A stop structure 92 is provided at the rear end of platform50 which limits the backward movement of the quench block assembly.

Platform 50 is secured by pin 100 to an upstanding bracket member 102which in turn is pivotally secured to intermediate member 104 bytransverse pin 106. Member 104 includes an arm 108 that projectslaterally from it which receives an adjusting screw 110. This adjustingscrew, at its upper end, engages platform 50 and when moved pivots thatplatform 50 about the axis defined by pin 100 in a level adjustmentoperation. At the rear end of intermediate member 104 is still anotheradjusting screw 112 the upper end which is secured to the rear end ofplatform 50 by block 114 so that rotation of screw 112 produces rotationof platform 50 about the axis defined by pin 106.

intermediate member 104 is supported on a base structure 120 byadjustment screw 122 and is guided by rods 124, 126. Adjustment screw122 is received in threaded relation by base 120 and is secured tointermediate member 104 so that rotation of screw 122 produces verticalmovement of platform 50 (via intermediate member 104). (While theseadjustments and particularly adjustment screw 122 are indicated asmanually operable be obvious appropriate adjustment drives such asservomotors may be utilized which respond to signals supplied over line134 from inspection unit 24 [FiG. 1].) Base 120 is secured on rails 130by bracket members 132.

The transition zone structure 16 includes a cylindrical tube 136 whichhas disposed in it an insert 140 that has a channel of U-shapedconfiguration as indicated in FIG. 2 that extends the full length of thetube and which is secured in position by four locking screws located inthe sides of the tube. The channel has two sidewalls 144, 146 and a basewall 148. The end of base wall 148 is an abrupt straight line surface.This insert is a material of low thermal conductivity and a satisfactorymaterial is Marinite an asbestos fiber material having an inorganicbinder.

In operation, strip is passed through the processing line at acontinuous and uniform rate of speed and is continually sensed for adish condition by a suitable gauging element, a satisfactory gaugingelement being disclosed in the copending patent application Ser. No.586,874, filed Oct. 14, 1966, now US. Pat. No. 3,465,571, and assignedto the same assignee as this application. Upon detection of a dishcondition the quench block assembly is lowered relative to the guidesurface 146 so that the strip steel 10 is forced over the sharp edge 150at the output end of insert 140. The upper surface of the strip steel issimilarly subjected to a transition of somewhat lesser magnitude by thefirst upper quench plate 64. This stressing of the strip is effective toremove the dish condition and result in a substantially flat steelstrip, the edge of which is suitable for sharpening by high-volume massproduction techniques to a durable, high-quality razor edge. in general,in the processing of this thin strip steel for commercially acceptablerazor blades it is preferred that the orientation of the dish conditionbe of concave downward configuration. With such configuration, the steelstrip is more uniformly guided by the insert in the transition zone andcreation of stains (oxidation) on the finished strip is minimized.

Thus the steel strip during the hardening process, is subjected tomechanical working at a point in the process where the condition of thesteel is such that it can be mechanically worked without adverse effect(such as marring) on its surface and yet the steel is in such conditionthat enables a dish condition to be removed through relatively minormanipulation of the steel prior to completion of the austenite tomartensite transformatiom While a particular embodiment of the Inventionhas been shown and described, various modifications thereof will be obvious to those skilled in the art and therefore it is not intended thatthe invention be limited to the disclosed embodiment or to detailsthereof and departures may be made therefrom within the spirit and scopeof the invention as defined in the claims.

What is claimed is:

1. A method of treating continuously moving steel strip for reducingtransverse curvature of the strip comprising the steps of heating saidstrip to produce austenite, cooling said strip rapidly to convert theaustenite to martensite, and during the conversion of austenite tomartensite, subjecting the opposite surfaces of said strip to adifferential stress by bending said strip over a relatively sharp edgedisposed generally perpendicularly to the direction of strip movement toreduce transverse curvature of the c8 strip so that the strip producedby said method is substantiaily flat.

2. The method as claimed in claim I wherein said strip is subjected tosaid differential stress when said strip is at a temperature of about320 F. and further including the step of passing said strip throughquench means immediately after said bending step.

3. The method as claimed in claim 1 and further including the steps ofinspecting the strip after it has cooled for transverse curvature andcontrolling the amount of differential stress to which said strip issubjected by varying the position of said relatively sharp edge as afunction of said inspection.

4. The method as claimed in claim 1 wherein said strip is a razor bladesteel strip in the the order of 0.0015 to 0.0039 inch in thickness, saidstrip is heated to a temperature in the order of 2,000 F and furtherincluding the step of passing said strip through quench meansimmediately after said bendin g step.

5. The method as claimed in claim 4 wherein said strip is subjected tosaid differential stress when said strip is at a temperature of about320 F.

6. The method as claimed in claim 5 and further including the steps ofinspecting the strip after it has cooled for transverse curvature andcontrolling the amount of differential stress to which said strip issubjected by varying the position of said relatively sharp edge as afunction of said inspection.

2. The method as claimed in claim 1 wherein said strip is subjected tosaid differential stress when said strip is at a temperature of about320* F. and further including the step of passing said strip throughquench means immediately after said bending step.
 3. The method asclaimed in claim 1 and further including the steps of inspecting thestrip after it has cooled for transverse curvature and controlling theamount of differential stress to which said strip is subjected byvarying the position of said relatively sharp edge as a function of saidinspection.
 4. The method as claimed in claim 1 wherein said strip is arazor blade steel strip in the order of 0.0015 to 0.0039 inch inthickness, said strip is heated to a temperature in the order of 2,000*F., and further including the step of passing said strip through quenchmeans immediately after said bending step.
 5. The method as claimed inclaim 4 wherein said strip is subjected to said differential stress whensaid strip is at a temperature of about 320* F.
 6. The method as claimedin claim 5 and further including the steps of inspecting the strip afterit has cooled for transverse curvature and controlling the amount ofdifferential stress to which said strip is subjected by varying theposition of said relatively sharp edge as a function of said inspection.